1) Field of the Invention
The present invention relates to a synthetic resin laminate having both polarization characteristics and photochromism characteristics, and specifically to a synthetic resin laminate having good appearance and excellent optical characteristics, which is used for glare-reducing materials, such as goggles and sun glasses for sport use, and can be readily produced and processed.
2) Prior Art
Goggles and sun glasses for sport use which have polarization characteristics exhibit excellent cutting characteristics against reflected light. Thus, their usefulness in outdoor activities such as marine sports, skiing and fishing has come to be noticed widely. Recently, their demand has suddenly expanded. Particularly, when a polycarbonate resin is used as the material for goggles and sun glasses, the demand is remarkable since the resin exhibits excellent impact resistance.
On the other hand, with the rapid development of excellent photochromic pigments, the characteristic of photochromic sun glasses to change transmittance depending upon surrounding brightness has also been remarkably improved. Therefore, photochromic sun glasses are becoming more popular.
Ideas concerning a synthetic resin glare-reducing material having both the function of changing transmittance depending on surrounding brightness and the function of preferentially blocking reflected light have been suggested. However, they have not been put into practice yet, because the process for producing synthetic resin glare-reducing materials was poor or properties of a product thus obtained were insufficient in the present production process.
For example, in the production of a polycarbonate lens described in Japanese Patent Publication No.7-94154, when a process comprising adding a photochromic pigment in the production of a polycarbonate sheet to be used is applied, a lens thus obtained is insufficient in both response speed and contrast. Also in resins other than a polycarbonate, a sheet with strength usable as a glare-reducing material usually causes problems that degradation of a photochromic pigment occurs during kneading; the kneading is troublesome and contrast or response speed of a product thus obtained is small.
In a process comprising coating a surface layer of a polarizing lens to be obtained in the process described in Japanese Patent Publication No.7-94154 with a photochromic pigment-containing resin, it is difficult to form a lens with good contrast since the thickness of an applicable coating layer is limited.
The present invention is to provide a synthetic resin laminate for a glare-reducing material having both polarization characteristic and photochromism characteristic which can be readily processed.
As a result of extensive trials and studies for various methods, the inventors have found that a laminate interposed between a resin layer having photochromism characteristics and a resin layer having polarization characteristics between two transparent synthetic resins exhibits not only excellent photochromism characteristics and polarization characteristics, but also processing into curved surfaces and injection molding can be readily performed. The laminate can also be produced in a very simple process.
That is, the present invention provides a synthetic resin laminate having both photochromism characteristics and polarization characteristics consisting essentially of (1) two transparent synthetic resin layers, (2) a resin layer having photochromism characteristics and a resin layer having polarization characteristics interposed between the two transparent synthetic resin layers and (3) an adhesive layer to adhere the resin layer having polarization characteristics and one of the two transparent synthetic resin layers, wherein the other one of the two transparent synthetic resin layers contacts the resin layer having photochromism characteristics and has a thickness of 50 xcexcm or above and a retardation value of 150 nm or below, or 3000 nm or above.
It is preferable that said one transparent synthetic resin contacts the adhesive layer having a thickness of 100 xcexcm or above.
It is preferable that said transparent synthetic resin is a polycarbonate resin. Also resins excellent in impact resistance, transparency and strength, other than a polycarbonate resin can be used.
Further, it is preferable that said resin layer having photochromism characteristics is a urethane resin layer containing a photochromic pigment(s).
It is preferable that said resin layer having polarization characteristics is a polarizing film.